REVIEW OF ASTRONOMY PUISEUX, 139 



spectra, and as yet unreproducible in the laboratory, are distributed 

 in series, and the structure of these series allows us to attribute to 

 them modified forms of these simple elements. The passage takes 

 place by discontinuous steps, corresponding to successive whole num- 

 bers of electrons. The transmutation of the nebula into the star 

 results less from a concentration of visible matter than from new 

 intraatomic configurations, the reverse of that which radioactive 

 matter undergoes in our laboratories and which has helium for its 

 final product. 



Nicholson, faithful to the traditions of Laplace, considers the 

 nebula as the primal form of matter in preference to the star, which 

 seems to him on the track toward a more complex structure. One is 

 tempted to regard the reverse route as probable if we consider two 

 incontestable facts: The practical irreversibility of the radioactive 

 transformation and the constant evolution of new stars tow^ard the 

 nebulous state. The artificial production of the nebula spectrum, if 

 it ever becomes possible, will of course throw light upon this problem 

 of the utmost importance to cosmogony. May we live long enough to 

 be witnesses of this conquest, the object of so much of our striving ! 



